The present invention relates to a pulley tyre and rim. More particularly, the pulley tyre and rim of the present invention are of the type having a peripheral recess or groove for receiving a rope or cable.
One form of prior art pulley is exemplified by the disclosure of GB 1125738 in which a rim is disclosed comprising a pair of opposed rim halves which are fixed to a hub to form the outer half of the pulley. Each rim half has bonded thereto a half tyre section. When the rims are bolted to the hub the half tyre sections form a complete tyre having a peripheral recess for accommodation of a rope or cable which is substantially concentric with the surface of the rim halves and hub. The interface between the two half tyre sections is prone to fracturing due to the lack of continuation of the section and the lack of support provided at the junction therebetween.
A further form of the prior art is the pulley tyre rim configuration disclosed in U.S. Pat. No. 5,019,019. This document discloses a single-piece annular tyre arranged to be held between a pair of rim halves. The tyre having provided therein a peripheral groove to locate a rope or cable during operation. Whilst this arrangement goes some way towards overcoming the abovementioned problem of fracturing of the half tyre sections there are additional problems associated with this arrangement. Significant levels of heat are generated during operation of pulleys of this type and this results in an increased flexibility in the tyre as the tyre is typically formed of an elastomeric material, for example polyurethane. The increased flexibility in the tyre can result in slipping of the tyre with respect to the rim halves thereby increasing wear and reducing the life of the tyre. Further, as the tyre wears there is an increasing tendency for it to lift away from the rim halves, upwardly and inwardly. This phenomenon is heightened when the tyre is worn thin and the rope or cable sits well down, or radially inwardly, in the peripheral recess or groove.
UK Patent Application GB 2036919 discloses a pulley assembly in which a half-tyre or liner has either a flange or a metal ring projecting inwardly therefrom and which is engaged by the bolts fixing the rim halves to the hub. This assembly is said to facilitate repair or replacement of the liner when worn.
U.S. Pat. 4,434,873 discloses an arrangement for the detection of worn linings of the sheaves in an elevator car. The groove forming surfaces of the plates forming the sheaves have provided thereon a plurality of projections extending into the non-metallic layers or tyre located thereon. These projections act to complete a circuit with the cable when the tyre is worn, thereby signaling that the tyre is worn.
Whilst the disclosures of GB 2036919 and U.S. Pat. No. 4,434,873 disclose arrangements in which there may be some restriction of rotational movement of the tyre relative to the rim, neither arrangement will combat the lifting away of the tyre from the rim when worn, enabling the use of softer tyre materials than might otherwise be possible.
The pulley tyre and rim of the present invention has one object thereof to overcome substantially the abovementioned problems associated with the prior art, or to at least provide a useful alternative thereto.
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In accordance with the present invention there is provided a pulley tyre and rim, the rim comprising two rim halves adapted to be mounted to a hub and to clampingly engage the pulley tyre, the pulley tyre having provided thereon one or more upstanding members, wherein the rim halves are adapted to receive the upstanding members when engaging the pulley tyre so as to minimise relative movement therebetween.
Preferably, the rim halves have complimentary apertures provided therein to receive therein or therethrough the upstanding members provided on the pulley type. The or each upstanding member is preferably provided on an axial surface of the tyre.
Still, preferably, a plurality of complimentary upstanding members and apertures are spaced substantially equidistant around at least one axial surface of the pulley tyre and rim halves. The plurality of complimentary upstanding members and apertures are preferably provided on both axial surfaces of the pulley tyre and rim halves.
The upstanding members preferably project into the apertures of the rim halves a distance allowing the engagement therebetween to at least substantially resist relative rotational and lifting movement of the pulley tyre with respect to the rim halves. The upstanding members are preferably proportioned to project through the apertures in the rim halves. Still preferably, the upstanding members have an enlarged head provided thereon to accentuate positive engagement therebetween. The or each upstanding member may be positioned substantially adjacent a peripheral edge of the axial face of the pulley tyre.
Weather lips may be provided at axial edges of a peripheral face of the pulley tyre, the lips arranged to cover peripheral edges of axial faces of each rim half.
In accordance with the present invention there is further provided a pulley tyre for use with a pulley tyre rim arranged to clampingly engage same, the pulley tyre being of annular configuration with a pair of axial faces and a peripheral face, the or each axial face of the pulley tyre having provided thereon at least one upstanding member arranged for positive engagement with the pulley tyre rim so as to minimise relative movement therebetween.
Preferably, a plurality of upstanding members are provided spaced substantially equidistant about each axial face of the pulley tyre.